Plans to extend the life of two reactors at the world's largest nuclear plant near Kincardine are being panned by critics.

They just wrapped up a multi-billion dollar refurbishment of two mothballed reactors at Bruce Power and soon decisions will have to be made on two more units.

"There isn't any real end date on the thing. When it reaches a point whetr it's no longer serviceable, you either repair it or replace it. It's a simple as that," says Frank Saunders of Bruce Power.

After running for nearly 30 years, two of the reactors at Bruce Power have reached their minimum design life. That's the amount of time it was assumed the unit's pressure tubes would be safe.

But the company thinks it can squeeze another five years out of them.

It has asked the Canadian Nuclear Safety Commission for permission to do so, which concerns some nuclear watchdog groups.

"Quebec was trying to decide whether to refurbish its reactors at the Gentilly-2 facility, and its president said he would no sooner run the plant beyond 210,000 effective full power hours than get in an airplane that hadn't been updated at its certified required flying life," says Theresa McClenaghan of the Canadian Environmental Law Association.

Frustrating McClenaghan further, the hearings into the extension were not open to the public.

"There are all kinds of serious, serious technical issues that have not been solved and so we really don't think these kinds of decisions should be made in secret," she says.

Saunders says Bruce Power has nothing to hide, extending the life of the pressure tubes and therefore the units is a safe and smart business decision, similar to replacing the tires on your car.

"When you bought the tires the manufacturer may have said about [40,000 kilometres]...but when you get to 40K you're going to look at the condition of the tires and if the tires aren't worn down past the wear bars, you're not going to replace them until it's time to replace them and it's the same with the plant."

A decision on the extension of the two units is expected sometime next week and public hearings will be held into the five-year extension of Bruce Power's licence to run the entire eight-unit fleet this spring.